Status category 1, "No category" - can this happen?

I’ve read in several places (for example here) that status categories are predefined and can’t be changed/added.
Checking the Get all status categories documentation, in the example response there are statuses with names that doesn’t exist and even with id 9 - this seems missleading.

Additionally when checking statuses for my test project it turns out that status ids starts with 2. So just to check I’ve tried in web browser and received following result:

{"self":"","id":1,"key":"undefined","colorName":"medium-gray","name":"No Category"}

Looks like there is fourth status category. It’s not possible to create status in this category with UI.

But the question is - can there be statuses with status category No Category?
After migration or other operations? Anyone met with such situation?